Organic semiconductor element

ABSTRACT

By introducing new concepts into a structure of a conventional organic semiconductor element and without using a conventional ultra thin film, an organic semiconductor element is provided which is more reliable and has higher yield. Further, efficiency is improved particularly in a photoelectronic device using an organic semiconductor. Between an anode and a cathode, there is provided an organic structure including alternately laminated organic thin film layer (functional organic thin film layer) realizing various functions by making an SCLC flow, and a conductive thin film layer (ohmic conductive thin film layer) imbued with a dark conductivity by doping it with an acceptor and a donor, or by the like method.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to an electronic device employingan organic semiconductor. More particularly, it relates to aphotoelectronic device such as a photoelectric conversion element and anEL element.

[0003] 2. Description of the Related Art

[0004] Compared to inorganic compounds, organic compounds include morevaried material systems, and through appropriate molecular design it ispossible to synthesize organic materials having various functionalities.Further, the organic compound is characterized in that films and thelike formed using the organic compound demonstrate great pliancy, andsuperior processability can also be achieved by polymerization. In lightof these advantages, in recent years, attention has been given tophotonics and electronics employing functional organic materials.

[0005] Photonic techniques which make use of photophysical qualities oforganic compounds have already played an important role in contemporaryindustrial techniques. For example, photosensitive materials, such as aphotoresist, have become indispensable in a photolithography technologyused for fine processing of semiconductors. In addition, since theorganic compounds themselves have properties of light absorption andconcomitant light emission (fluorescence or phosphorescence), they haveconsiderable applicability as light emitting materials such as laserpigments and the like.

[0006] On the other hand, since organic compounds do not have carriersthemselves, they essentially have superior insulation properties.Therefore, in the field of electronics where the electrical propertiesof organic materials are utilized, the main conventional use of organiccompounds is insulators, where organic compounds are used as insulatingmaterials, protective materials and covering materials.

[0007] However, there are means for making massive amounts of electricalcurrent flow in the organic materials which is essentially insulators,and they are starting to be put to practical use in the electronicsfield. The “means” discussed here can be broadly divided into twocategories.

[0008] The first of these, represented by conductive polymers, is meansin which a π-conjugate system organic compound is doped with an acceptor(electron acceptor) or a donor (electron donor) to give the π-conjugatesystem organic compound a carrier (Reference 1: Hideki Shirakawa, EdwinJ. Louis, Alan G. MacDiarmid, Chwan K. Chiang, and Alan J. Heeger,“Synthesis of Electrically Conducting Organic Polymers: HalogenDerivatives of Polyacetyrene, (CH)_(x)”, Chem. Comm., 1977, 16,578-580). By increasing the doping amount, the carrier will increase upto a certain area. Therefore, its dark conductivity will also increasetogether with this, so that significant electricity will be made toflow.

[0009] Since the amount of the electrical flow can reach the level of anormal semiconductor or more, a group of materials which exhibit thisbehavior can be referred to as organic semiconductors (or, in somecases, organic conductors).

[0010] This means of doping the acceptor/donor to improve the darkconductivity to make the electrical current flow in the organic materialis already being applied in part of the electronics field. Examplesthereof include a rechargeable storage battery using polyaniline orpolyacene and an electric field condenser using polypyrrole.

[0011] The other means for making massive electrical current flow in theorganic material uses an SCLC (Space Charge Limited Current). The SCLCis an electrical current which is made to flow by injecting a spacecharge from the outside and moving it, the current density of which isexpressed by Child's Law, i.e., Formula 1, shown below. In the formula,J denotes a current density, ε denotes a relative dielectric constant,ε₀ denotes a vacuum dielectric constant, μ denotes a carrier mobility, Vdenotes a voltage, and d denotes a distance (hereinafter, referred to as“thickness”) between electrodes applied with the voltage V:

J=9/8·εε₀ μ·V ² /d ³  Formula 1

[0012] Note that the SCLC is expressed by Formula 1 in which no carriertrap when the SCLC flows is assumed at all. The electric current limitedby the carrier trap is referred to as a TCLC (Trap Charge LimitedCurrent), and it is proportionate to a power of the voltage, but boththe SCLC and the TCLC are currents that are subject to bulk limitations.Therefore, both the SCLC and the TCLC are dealt with in the same wayhereinbelow.

[0013] Here, for comparison, Formula 2 is shown as a formula expressingthe current density when an Ohm current flows according to Ohm's Law. σdenotes a conductivity, and E denotes an electric field strength:

J=σE=σ·V/d  Formula 2

[0014] In Formula 2, since the conductivity σ is expressed as σ=neμ(where n denotes a carrier density, and e denotes an electric charge),the carrier density is included in the factors governing the amount ofthe electrical current that flows. Therefore, in an organic materialhaving a certain degree of carrier mobility, as long as the material'scarrier density is not increased by doping as described above, the Ohmcurrent will not flow in a material which normally does not have fewcarriers.

[0015] However, as is seen in Formula 1, the factors which determine theSCLC are the dielectric constant, the carrier mobility, the voltage, andthe thickness. The carrier density is irrelevant. In other words, evenin the case of an organic material insulator with no carrier, by makingthe thickness d sufficiently small, and by selecting a material with asignificant carrier mobility μ, it becomes possible to inject a carrierfrom the outside to make the current flow.

[0016] Even when this means is used, the current flow amount can reachthe level of a normal semiconductor or more. Thus, an organic materialwith a great carrier mobility μ, in other words, an organic materialcapable of latently transporting a carrier, can be called an “organicsemiconductor”.

[0017] Incidentally, even among organic semiconductor elements which usethe SCLC as described above, organic electroluminescent elements(hereinafter, referred to as “organic EL elements”) which use both thephotonic and electrical qualities of functional organic material asphotoelectronic devices, have particularly demonstrated remarkableadvancement in recent years.

[0018] The most basic structure of the organic EL element was reportedby W. Tang, et al. in 1987 (Reference 2: C. W. Tang and S. A. Vanslyke,“Organic electroluminescent diodes”, Applied Physics Letters, Vol. 51,No. 12, 913-915 (1987)). The element reported in Reference 2 is a typeof diode element in which electrodes sandwich an organic thin filmhaving a total thickness of approximately 100 nm and being constitutedby laminating a hole-transporting organic compound and anelectron-transporting organic compound, and the element uses a lightemitting material (fluorescent material) as the electron-transportingcompound. By applying voltage to the element, light-emission can beachieved as from a light emitting diode.

[0019] The light-emission mechanism is considered to work as follows.That is, by applying the voltage to the organic thin film sandwiched bythe electrodes, the hole and the electron injected from the electrodesare recombined inside the organic thin film to form an excited molecule(hereinafter, referred to as a “molecular exciton”), and light isemitted when this molecular exciton returns to its base state.

[0020] Note that, types of molecular excitons formed by the organiccompound can include a singlet excited state and a triplet excitedstate, and the base state is normally the singlet state. Therefore,emitted light from the singlet excited state is referred to asfluorescent light, and the emitted light from the triplet excited stateis referred to as phosphorescent light. The discussion in thisspecification covers cases of contribution to the emitted light fromboth of the excited states.

[0021] In the case of the organic EL element described above, theorganic thin film is normally formed as a thin film having a thicknessof about 100 to 200 nm. Further, since the organic EL element is aself-luminous element in which light is emitted from the organic thinfilm itself, there is no need for such a back light as used in aconventional liquid crystal display. Therefore, the organic EL elementhas a great advantage in that it can be manufactured to be extremelythin and lightweight.

[0022] Further, in the thin film having a thickness of about 100 to 200nm, for example, the time from when the carrier is injected to when therecombination occurs is approximately several tens of nanoseconds, giventhe carrier mobility exhibited by the organic thin film. Even when thetime required by for the process form the recombination of the carrierto the emission of the light, it is less than an order of microsecondsbefore the light emission. Therefore, one characteristic of the organicthin film is that response time thereof is extremely fast.

[0023] Because of the above-mentioned properties of thinness andlightweightness, the quick response time, and the like, the organic ELelement is receiving attention as a next generation flat panel displayelement. Further, since it is self-luminous and its visible range isbroad, its visibility is relatively good and it is considered effectiveas an element used in display screens of portable devices.

[0024] Further, in addition to the organic EL element, an organic solarbattery is another representative example of an organic semiconductorelement using organic material (i.e., an organic semiconductor) capableof transporting carriers latently, which is to say having a certaindegree of carrier mobility.

[0025] In short, the organic solar battery utilizes an oppositestructure to the organic EL element. That is, its structure is similarto the most basic structure of the organic EL element, where the organicthin film having the two-layer structure is sandwiched by electrodes(Reference 3: C. W. Tang, “Two-layer organic photovoltaic cell”, AppliedPhysics Letters, vol. 48, No. 2, 183-185 (1986)). A photoelectriccurrent generated by causing light to be absorbed into the organic thinfilm is used to obtain an electromotive force. The electric current thatflows at this time can be understood as follows: the carrier generatedby the light flows due to the carrier mobility present in the organicmaterial.

[0026] In this way, the organic material, which was considered as havingno purpose in the electronics field other than its original purpose asan insulator, can be made to perform central functionalities in variouselectronic devices and photoelectronic devices by skillfully devisingthe organic semiconductor. Accordingly, research in organicsemiconductors has become robust at present.

[0027] Description has been made above regarding two methods using theorganic semiconductor as means for flowing the electric current to theorganic material which is essentially an insulator. However, each ofthese two methods has a different problem.

[0028] First, in the case where the acceptor and the donor are doped tothe organic semiconductor to increase the carrier densities, theconductivity is actually improved but the organic semiconductor itselfloses its own physical properties (light absorption, phosphorescence,etc.) which it originally had. For example, when a phosphorescent-lightemitting π-conjugate system polymer material is doped with theacceptor/donor, its conductivity increases but it stops emitting light.Therefore, in exchange for obtaining the functionality of conductivity,the other various functionalities which the organic material possessesare sacrificed.

[0029] Further, although there is an advantage in that variousconductivities can be achieved by adjusting a doping amount of theacceptor or the donor, no matter how much acceptor and donor are dopedto increase the carrier, it is difficult to constantly obtain a carrierdensity equivalent to a metal or of an inorganic compound that isequivalent to a metal (e.g., nitride titan or other such inorganiccompound conductor). In other words, with respect to conductivity, it isextremely difficult to surpass an inorganic material, except for inseveral examples. Thus, the only remaining advantage is that the organicmaterial is extremely workable and pliant.

[0030] On the other hand, in the case where the SCLC (hereinafter, SCLCincludes a photoelectric current) is made to flow to the organicsemiconductor, the physical properties that the organic semiconductororiginally had are not lost. A representative example of such is noneother than the organic EL element, in which the light emission from thefluorescent material (or phosphorescent material) is utilized even whenthe electric current is made to flow. The organic solar battery alsoutilizes the functionality of light absorption by the organicsemiconductor.

[0031] However, as can be understood by looking at Formula 1, since theSCLC is inversely proportionate to the 3rd power of the thickness d, theSCLC can only be made to flow through a structure consisting ofelectrodes sandwiched to both surfaces of extremely thin films. Morespecifically, in light of the general carrier mobility of organicmaterials, the structure must be an ultra thin film of approximately 100nm to 200 nm.

[0032] It is true, however, that by adopting the above-mentioned ultrathin film structure, a significant amount of SCLC can be made to flow atlow voltage. One reason why the organic EL element such as the onediscussed in Reference 2 is successful is because the thickness of itsorganic thin film is designed as a uniformly ultra thin film having athickness of approximately 100 nm.

[0033] However, the fact that the thickness d must be made extremelythin actually becomes the biggest problem when the SCLC is made to flow.First, in the 100 nm thin film, it is easy for pinholes and other suchdefects to develop, and short circuits and other such problems occur dueto these, causing a concern that yield may deteriorate. Further, notonly does the mechanical strength of the thin film decline, but also themanufacturing process itself is restricted because the film must be anultra thin film.

[0034] Further, when the SCLC is used as the electric current, thephysical properties that the organic semiconductor itself originallypossessed are not lost, and there is an advantage in that variousfunctionalities can be produced. However, deterioration of thefunctionality of the organic semiconductor is accelerated by making theSCLC flow. For example, looking at the organic EL element as an example,it is known that the lifetime of the element (i.e., the half-life of thebrightness level of the emitted light) deteriorates almost in inverseproportion to its original brightness, or, in other words, to the amountof electrical current that is made to flow (Reference 4: Yoshiharu SATO,“The Japan Society of Applied Physics/Organic Molecular Electronics andBioelectronics”, vol. 11, No. 1 (2000), 86-99).

[0035] As described above, in the device where the acceptor or the donoris doped to produce conductivity, functionalities other than theconductivity are lost. Further, in the device where the SCLC is used toproduce the conductivity, the flowing of massive amounts of anelectrical current through the ultra thin film becomes a cause ofproblems regarding the element's reliability and the like.

[0036] Incidentally, in photoelectronic devices using the organicsemiconductors, such as organic EL elements and organic solar batteries,there is also a problem with respect to efficiency.

[0037] The organic EL element will be discussed as an example. The lightemitting mechanism of the organic EL element is that the injected holeand electron recombine with each other to be converted into light.Therefore, theoretically, it is possible to extract at most one photonfrom the recombination of one hole and one electron, and it is not bepossible to extract a plurality of photons. That is, the internalquantum efficiency (the number of emitted photons with respect injectedcarriers) should be at most 1.

[0038] However, in reality, it is difficult to bring the internalquantum efficiency close to 1. For example, in the case of the organicEL element using the fluorescent material as the light emitting body,the statistical ratio of generation for the singlet excited state (S*)and the triplet excited state (T*) is considered to be S*:T*=1:3(Reference 5: Tetsuo TSUTSUI, “Textbook of the 3rd seminar at Divisionof Organic Molecular Electronics and Bioelectronics, The Japan Societyof Applied Physics”, p. 31 (1993)). Therefore, the theoretical limit ofthe internal quantum efficiency is 0.25. Furthermore, as long as thefluorescent quantum yield from the fluorescent material is not φ_(f),the internal quantum efficiency will drop even lower than 0.25.

[0039] In recent years, attempts have been made to use phosphorescentmaterials to use the light emission from the triplet excited state tobring the internal quantum efficiency's theoretical limit close to 0.75to 1, and the efficiency actually surpassing that of fluorescentmaterial has been achieved. However, in order to achieve this, it isnecessary to use a phosphorescent material with a high phosphorescentquantum efficiency φ_(p). Therefore, the range of selection for thematerial is unavoidably restricted. This is because organic compoundsthat can emit phosphorescent light at room temperature are extremelyrare.

[0040] In other words, if means could be structured for improving theelectrical current efficiency (the brightness level generated inrelation to the electrical current) of the organic EL element, thiswould be a great innovation. If the electrical current efficiency isimproved, a greater level of brightness can be produced with a smallerelectrical current. Conversely, since the electrical current can bereduced for achieving a certain brightness level, the deteriorationcaused by the massive amount of electrical current made to flow to theultra thin film as described above can be reduced.

[0041] The inverse structure of the organic EL element, which is to saythe photoelectric conversion such as in the organic solar battery, isinefficient at present. As described above, in the organic solar batteryusing the conventional organic semiconductor, the electrical currentdoes not flow if the ultra thin film is not used. Therefore,electromotive force is not produced, either. However, when the ultrathin film is adopted, a problem arises in that the light absorptionefficiency is poor (i.e., the light cannot be completely absorbed). Thisproblem is considered to be the largest reason for the poor efficiency.

[0042] In light of the foregoing discussion, the electronic device usingthe organic semiconductor has a shortcoming in that when the massiveelectrical current is made to flow in a device utilizing the physicalproperties that are unique to the organic material, the reliability andyield from the device is influenced unfavorably. Furthermore,particularly in the photoelectronic device, the efficiency of the deviceis poor. These problems basically can be said to arise from the “ultrathin film” structure of the conventional organic semiconductor element.

SUMMARY OF THE INVENTION

[0043] Therefore, an object of the present invention is to introduce anew concept to the structure of the conventional organic semiconductorelement, to provide an organic semiconductor element with not onlygreater reliability but also higher yield, without using theconventional ultra thin film. Another object of the present invention isto improve the efficiency of the photoelectronic device using theorganic semiconductor.

[0044] The inventor of the present invention, as a result of repeatedintense studies, has devised means capable of achieving theabove-mentioned object by combining an organic semiconductor that isdoped with an acceptor or a donor to make it conductive, and an organicsemiconductor in which an SCLC is used to achieve the conductivity. Themost basic structure thereof is shown in FIG. 1.

[0045]FIG. 1 shows an organic semiconductor element comprised of anorganic structure in which, between an anode and a cathode, there arealternatively laminated an organic thin film layer (referred to as a“functional organic thin film layer” in the present specification) forrealizing various functionalities by flowing an SCLC, and a conductivethin film layer in a floating state in which a dark conductivity isachieved by doping the acceptor or donor, or by another method.

[0046] What is important here, is that the conductive thin film layershould be connected substantially ohmically to the functional organicthin film layer (in this case, the conductive thin film layer isparticularly referred to as an “ohmic conductive thin film layer”). Inother words, obstructions between the conductive thin film layer and thefunctional organic thin film layer should be eliminated or extremelyminimized.

[0047] By adopting the above structure, holes and electrons are easilyinjected each from the ohmic conductive thin film layers into each ofthe functional organic thin film layers. For example, a conceptualdiagram of an element shown in FIG. 1 as n=2 is shown in FIGS. 2A and2B. In FIGS. 2A and 2B, when an electrical voltage is applied betweenthe anode and the cathode, electrons are easily injected from a firstohmic conductive thin film layer into a first functional organic thinfilm layer, and the holes are easily injected from the first ohmicconductive thin film layer into a second functional organic thin filmlayer. When viewed from an external circuit, a hole moves from the anodetoward the cathode, and an electron moves from the cathode toward theanode (FIG. 2A). However, it can also be understood that both theelectron and the hole flow from the ohmic conductive thin film layerback toward the opposite directions (FIG. 2B).

[0048] Here, by making each functional organic thin film layer to have athickness of 100 nm to 200 nm or smaller, the carrier injected into eachfunctional organic thin film layer can be made to flow as the SCLC. Thatis, in each functional organic thin film layer, a functionality (such aslight emission or the like) derived from the inherent physicality of theorganic material can be realized.

[0049] Moreover, when the basic structure of the present invention isapplied, the organic structure can be made to have any degree ofthickness, which is extremely useful. In other words, assume that in theconventional element (in which a functional organic thin film layer 303is sandwiched between a cathode 301 and a anode 302), a given electricalvoltage V is applied to the film thickness d to thereby obtain anelectrical current density of J (FIG. 3A). Here, in the case of thepresent invention (FIG. 3B) with the alternatively laminated n number offunctional organic thin film layers 303 similarly having film thicknessd and (n−1) number of ohmic conductive thin film layers 304, where itwas only possible to flow the SCLC into the thickness d (which was 100nm to 200 nm in the conventional art), the present invention appearsequivalent to flowing an SCLC having the current density J to a filmthickness nd, just as in the case shown in FIG. 3A. In other words, theeffect is that of FIG. 3C, but this is impossible in the conventionalart because no matter how much voltage is applied, the SCLC suddenlystops flowing if the film thickness becomes very thick.

[0050] Of course, this simply means only that an electrical voltage nVis required. However, the electronic devices using the organicsemiconductor can easily overcome the problem in that by utilizing theorganic material's inherent physical properties, when a massive amountof electrical current is made to flow, there is a negative effect on thereliability and the yield of the device.

[0051] Thus, by providing the organic structure with the alternatelylaminated functional organic thin film layer and conductive thin filmlayer, the organic semiconductor element can make the SCLC flow ingreater film thickness than in the conventional art. This concept didnot exist until now. This concept can obviously be applied in organic ELelements where the SCLC is made to flow to achieve light emission and inorganic solar batteries which utilize a photoelectric current and aresaid to have the opposite mechanism of the organic EL elements. Theconcept can also be applied broadly to other organic semiconductorelements.

[0052] Therefore, according to the present invention, there is providedan organic semiconductor element comprised of an organic structureformed by sequentially laminating an n number of functional organic thinfilm layers (where n is an integer equal to or greater than 2)consisting of a first through an n-th functional organic thin filmlayers between an anode and a cathode, characterized in that: aconductive thin film layer in a floating state is without exceptionformed between a k-th functional organic thin film layer (where k is aninteger of 1≦k≦(n−1)) and a (k+1)th functional organic thin film layer;and each of the conductive thin film layers ohmically contacts with eachof the functional organic thin film layer.

[0053] In this case, as the conductive thin film layer, it is preferableto use an organic compound instead of using a metal or a conductiveinorganic compound. Particularly in the case of the photoelectronicdevice which requires transparency, it is preferable to use the organiccompound.

[0054] Therefore, according to the present invention, there is providedan organic semiconductor element comprised of an organic structureformed by sequentially laminating an n number of functional organic thinfilm layers (where n is an integer equal to or greater than 2)consisting of a first through an n-th functional organic thin filmlayers between an anode and a cathode, characterized in that: aconductive thin film layer in a floating state which includes an organiccompound is without exception formed between a k-th functional organicthin film layer (where k is an integer of 1≦k≦(n−1)) and a (k+1)thfunctional organic thin film layer; and each of the conductive thin filmlayers ohmically contacts with each of the functional organic thin filmlayer.

[0055] Also, in order to contact the conductive thin film layer with thefunctional organic thin film layer ohmically or in a substantiallyequivalent manner, as described above, it is important to adopt themeans in which the conductive thin film layer is formed of the organiccompound and the layer is doped with the acceptor or the donor.

[0056] Therefore, according to the present invention, there is providedan organic semiconductor element comprised of an organic structureformed by sequentially laminating an n number of functional organic thinfilm layers (where n is an integer equal to or greater than 2)consisting of a first through an n-th functional organic thin filmlayers between an anode and a cathode, characterized in that: aconductive thin film layer in a floating state which includes an organiccompound is without exception formed between a k-th functional organicthin film layer (where k is an integer of 1≦k≦(n−1)) and a (k+1)thfunctional organic thin film layer; and each of the conductive thin filmlayers contains at least one of an acceptor and a donor for the organiccompound.

[0057] Also, according to the present invention, there is provided anorganic semiconductor element comprised of an organic structure formedby sequentially laminating an n number of functional organic thin filmlayers (where n is an integer equal to or greater than 2) consisting ofa first through an n-th functional organic thin film layers between ananode and a cathode, characterized in that: a conductive thin film layerin a floating state which includes an organic compound is withoutexception formed between a k-th functional organic thin film layer(where k is an integer of 1≦k≦(n−1)) and a (k+1)th functional organicthin film layer; and each of the conductive thin film layers containsboth of an acceptor and a donor for the organic compound.

[0058] Note that, when the conductive thin film layer is doped with theacceptor or the donor, the organic compound used in the functionalorganic thin film layer and the organic compound used in the conductivethin film layer are connected with the same thing (i.e., the organiccompound used in the functional organic thin film layer is included intothe conductive thin film layer, and the conductive thin film layer isdoped with the acceptor or the donor). This enables the element to bemanufactured according to a simple process.

[0059] Incidentally, in the case where both the acceptor and the donorare included in the conductive thin film layer, it is preferable that:the conductive thin film layer be structured by laminating a first layerformed by adding an acceptor to the organic compound, and a second layerformed by adding a donor to an organic compound that is the same as theorganic compound; and the first layer be positioned closer to a cathodeside than the second layer.

[0060] Also, in such a case, it is preferable that the organic compoundused in the functional organic thin film layer and the organic compoundused in the conductive thin film layer be connected with the same thing.

[0061] Incidentally, in the case where both the acceptor and the donorare included in the conductive thin film layer, it is also preferablethat: the conductive thin film layer be structured by laminating a firstlayer formed by adding an acceptor to a first organic compound, and asecond layer formed by adding a donor to a second organic compound thatis different from the first organic compound; and the first layer bepositioned closer to a cathode side than the second layer.

[0062] Also, in such a case, it is preferable that the organic compoundused in the functional organic thin film layer and the organic compoundused in the first layer be connected with the same thing. Also, it ispreferable that the organic compound used in the functional organic thinfilm layer and the organic compound used in the second layer beconnected with the same thing.

[0063] The structure of the functional organic thin film layer may bemanufactured using a bipolar organic compound, or by combining monopolarorganic compounds by laminating a hole transporting layer and anelectron transporting layer, for example.

[0064] The element structure described above is extremely useful amongorganic semiconductor elements particularly because in thephotoelectronics field it can increase light emission efficiency andlight absorption efficiency. That is, by structuring the functionalorganic thin film layer with the organic compound that exhibits lightemission by flowing the electrical current, the organic EL element withhigh reliability and good efficiency can be created. Further, bystructuring the functional organic thin film layer with the organiccompound which generates the photoelectric current (i.e., generates theelectromotive force) by absorbing light, the organic solar battery withhigh reliability and good efficiency can be created.

[0065] Therefore, the present invention includes everything related tothe organic semiconductor element in which the functional organic thinfilm layer described above has the structure capable of realizing theorganic EL element functionality and the organic solar batteryfunctionality.

[0066] Note that, particularly in the organic EL element, in the casewhere the functional organic thin film layer is structured with thebipolar organic compound, the bipolar organic compound preferablyincludes a high molecular compound having a π-conjugate system. Further,for the conductive thin film layer as well, it is desirable to use amethod in which the high molecular compound having an π-conjugate systemis used and the layer is doped with the acceptor or the donor to improvethe dark conductivity. Alternatively, for the conductive thin filmlayer, it is also possible to use a conductive high molecular compoundwith the acceptor or donor added thereto.

[0067] Further, in the organic EL element, in the case where, forexample, the hole transporting layer made of a hole transportingmaterial, and the electron transporting layer made of an electrontransporting material, are laminated to structure the functional organicthin film layer by combining monopolar organic compounds, the conductivethin film layer should also be made using at least one of the holetransporting material and the electron transporting material, and thelayers should be doped with the acceptor and donor to increase the darkconductivity. Alternatively, it is also possible to use both the holetransporting material and the electron transporting material. In morespecific terms, this refers to a method in which a donor-doped layer ofthe electron transporting material used in the functional organic thinfilm layer, and an acceptor-doped layer of the hole transportingmaterial used in the functional organic thin film layer, are laminatedupon each other in a structure used as the conductive thin film layer.

[0068] The structure of the functional organic thin film layer when usedin the organic solar battery is the same as when used in the organic ELelement. That is, in the organic solar battery, in the case where thefunctional organic thin film layer is structured with the bipolarorganic compound, the bipolar organic compound preferably includes ahigh molecular compound having the π-conjugate system. Further, for theconductive thin film layer as well, it is desirable to use a method inwhich the high molecular compound having the π-conjugate system is usedand the layer is doped with the acceptor or the donor to improve thedark conductivity. Alternatively, for the conductive thin film layer, itis also possible to use the conductive high molecular compound with theacceptor or donor added thereto.

[0069] Further, in the organic solar battery, in the case where, forexample, the layer made of the hole transporting material, and the layermade of the electron transporting material, are laminated to structurethe functional organic thin film layer by combining monopolar organiccompounds, the conductive thin film layer should also be made using atleast one of the hole transporting material and the electrontransporting material, and the layers should be doped with the acceptorand donor to increase the dark conductivity. Alternatively, it is alsopossible to use both the hole transporting material and the electrontransporting material. In more specific terms, this refers to a methodin which the donor-doped layer of the electron transporting materialused in the functional organic thin film layer, and the acceptor-dopedlayer of the hole transporting material used in the functional organicthin film layer are laminated upon each other in the structure used asthe conductive thin film layer.

[0070] Note that, if the carrier can be injected into all the conductivethin film layers (ohmic conductive thin film layers) described above,then it is not necessary to reduce sheet resistance in any of them.Accordingly, a conductivity rate of 10⁻¹⁰ S/m² or greater is sufficient.

BRIEF DESCRIPTION OF THE DRAWINGS

[0071] In the accompanying drawings:

[0072]FIG. 1 shows a basic structure of the present invention;

[0073]FIGS. 2A and 2B show concepts of the present invention;

[0074]FIGS. 3A to 3C show effects produced by the present invention;

[0075]FIGS. 4A and 4B illustrate theory behind improvement in electricalcurrent efficiency;

[0076]FIG. 5 shows theory behind improvement in the electrical currentefficiency;

[0077]FIGS. 6A and 6B depict conventional organic EL elements;

[0078]FIG. 7 shows an organic EL element according to the presentinvention;

[0079]FIG. 8 shows a specific example of an organic EL element accordingto the present invention;

[0080]FIG. 9 shows a specific example of an organic EL element accordingto the present invention; and

[0081]FIG. 10 shows a specific example of an organic EL elementaccording to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0082] Hereinafter, detailed explanation is made with respect toembodiments of the present invention, using an organic EL element and anorganic solar battery as examples. Note that, with respect to theorganic EL element, in order to achieve light emission, it is sufficientif at least one of an anode and a cathode is made transparent. However,in accordance with this embodiment mode, description is made of anelement structure in which a transparent anode is formed on a substrateto achieve the light from the anode side. In actuality, the presentinvention may be applied in a structure in which the cathode is formedonto the substrate to achieve the light from the cathode side, and in astructure in which the light is achieved from an opposite side from thesubstrate, and in a structure in which the light is achieved from boththe electrodes on both sides. In the organic solar battery as well, inorder to make the battery absorb light, any one side of the element maybe made transparent.

[0083] First, in the organic EL element, as means for overcoming thepoor reliability deriving from the ultra thin film and also forimproving the proportion of light emitted in relation to the electricalcurrent (i.e., the electrical current efficiency), in order to achieve asimple device structure, the organic EL element may be connectedserially, for example. This will be explained below.

[0084] As shown in, FIG. 4A, assume an organic EL element D₁, in whichapplying a certain electrical voltage V₁ causes an electric current withan electric density J₁ to flow and light is emitted by a light energyper unit surface area L₁ (i.e., photons having certain amounts of energyare emitted, and the light energy is equivalent to the product of thatenergy multiplied by the number of photons). At this time, a powerefficiency φe₁ (this refers to the light emission energy with respect tothe electrical energy (electrical power) that was given, and it meansthe same thing as an “energy conversion rate”) is given in the followingformula:

φe ₁ =L ₁/(J ₁ ·V ₁)  Formula 3

[0085] Next, a case will be considered in which an organic EL element D₂that is exactly equivalent to the organic EL element D₁ is connected tothe organic EL element D₁ serially (See FIG. 4B). Note that, a contactpoint C₁ connects the two elements D₁ and D₂ together ohmically.

[0086] Here, the elements as a whole (i.e., element D_(all) having thestructure consisting of D₁ and D₂ connected to each other) are appliedwith a voltage V₂ (=2V₁) that is double the voltage that was applied inFIG. 4A. Then, since D₁ and D₂ are equivalent to each other, the voltageV₁ is applied to D₁ and to D₂, respectively, as shown in FIG. 4B, andthe shared electrical current density J₁ flows. Therefore, since D₁ andD₂ each emit light with the light energy L₁, double the light energy 2L₁can be obtained from the elements as a whole D_(all).

[0087] The power efficiency φe₂ at this time is given in the followingformula:

φe ₂=2L ₁/(J ₁·2V ₁)=L1/(J·V ₁)  Formula 4

[0088] As can be understood by comparing the above-mentioned Formula 3and the above-mentioned Formula 4, there is no difference between FIG.4A and FIG. 4B in terms of the power efficiency, and the law of energyconservation in which V₁ and J₁ are converted to L₁ is being obeyed.However, the current efficiency appears to increase twofold, i.e., L₁/J₁is increased to 2L₁/J₁. This has a significant meaning for the organicEL element. That is, by increasing the organic EL elements connectedserially and by applying more voltage in proportion to the number ofelements that were increased and maintaining the current density at afixed level, it becomes possible to increase the electrical currentefficiency.

[0089] Examining this concept more generally, when n number of theentirely equivalent organic EL elements are ohmically connected, it ispossible to achieve n times the brightness level by maintaining thecurrent density at a fixed level and increasing the electrical voltageby n times. This property derives from the proportional relationshipbetween the brightness level and the electrical current density level inthe organic EL element.

[0090] Of course, even in the case where different organic EL elementsare connected serially, the brightness level emitted from each of theorganic EL elements will be different. However, by significantlyincreasing the voltage, it becomes possible to extract more brightnessthan in the case of a single organic EL element. A conceptual diagram ofthis is shown in FIG. 5.

[0091] As shown in FIG. 5, when the different organic EL elements D₁ andD₂ are connected serially and one of the organic EL elements (either D₁or D₂) is applied with a higher voltage V₁+V₂ than the necessary voltage(either V₁ or V₂) to create the electrical current J₁, a brightnesslevel L₁+L₂ (>L₁, L₂) can be produced with the current J₁.

[0092] At this time, by configuring, for example, D₁ as a blue lightemitting element and D₂ as a yellow light emitting element, if colormixing can be performed, then a white color light emission will occur.Therefore, this enables a white color emitting element in which theelectrical current efficiency is higher, and therefore the longevity ofthe element is higher than in the conventional art.

[0093] As described above, by ohmically connecting the elementsserially, the apparent electrical current efficiency is improved andgreater brightness can be obtained with a smaller electrical current.This means that it is possible to make the necessary electrical currentfor emission of the same level of brightness is kept smaller than in theconventional art. Furthermore, as long as a significant electricalvoltage can be applied, it is possible to connect however many organicEL elements as may be needed, and the overall film thickness can be madethick.

[0094] However, as described above, a problem occurs even in the casewhere the organic EL elements are simply connected serially. The problemderives from the electrodes for the organic EL elements and from theelement structure, which will be explained using FIG. 6. FIG. 6A shows across-sectional view of the organic EL element D₁ shown in FIG. 4A, andFIG. 6B shows a cross sectional view of all the elements D_(all) shownin FIG. 4B, in a schematic manner.

[0095] The basic structure (FIG. 6A) of the normal organic EL element ismanufactured by providing a transparent electrode 602 onto a substrate601 (here, the electrode is an anode, and an ITO or the like isgenerally used for this), a functional organic thin film layer(hereinafter, referred to as an “organic EL layer”) 604 for performinglight emission by flowing an electrical current is then formed and acathode 603 is then provided. With this structure, light can be producedfrom the transparent electrode (the anode) 602. The cathode 603 may be acathode which normally employs both a metallic electrode with a low workfunction, or an electron injecting cathode buffer layer, along with ametallic conductive film (such as aluminum or the like).

[0096] When two organic EL elements having the structure described aboveare connected simply serially (as shown in FIG. 6B), the structure willinclude a first transparent electrode (cathode) 602 a, a first organicEL layer 604 a, a first cathode 603 a, a second organic EL layer 604 b,a second organic EL layer 604 b, and a second cathode 603 b, which arelaminated in this order from the lower side. Then, the light emitted bythe second organic EL layer 604 b cannot be transmitted through becausethe first cathode 603 a which is metal, and thus the light cannot betaken out of the element. Therefore, it becomes impossible to do suchinnovations as mixing the light emission from the upper and the lowerorganic EL elements to produce the white color light.

[0097] For example, a technique using transparent ITO cathodes for boththe anode and the cathode has also be reported (Reference 6: G.Parthasarathy, P. E. Burrows, V. Khalfin, V G. Kozlov, and S. R.Forrest, “A metal-free cathode for organic semiconductor devices”, J.Appl. Phys., 72, 2138-2140 (1998)). By using this, the first cathode 603a can be made transparent. Therefore, it becomes possible to bring outthe light emitted from the second organic EL layer 604 b. However, sincethe ITOs are mainly formed by sputtering, there is a concern that theorganic EL layer 604 a will suffer damage. Further, the process alsobecomes cumbersome because the application of the organic EL layer bydeposition and the application of the ITO by sputtering have to berepeated.

[0098] In order to overcome this problem, a more desirable embodimenthas a structure such as shown in FIG. 7, for example, in which theelectrical current efficiency can be improved using a concept similarconnecting the elements serially to improve the electrical currentefficiency, and also the element transparency issue can be clearedwithout a problem.

[0099]FIG. 7 shows a structure in which a first organic EL layer 704 a,a first conductive thin film layer 705 a, a second organic EL layer 704b, and a cathode 703 are laminated in this order on a transparentelectrode (anode) 702 that is provided to a substrate 701. In thisstructure, by applying a material in which the acceptor or the donor hasbeen applied to the organic semiconductor, the first semiconductor thinfilm layer 705 a can be connected almost ohmically to the organic ELlayer (i.e., the hole carrier and the electron carriers can beinjected), and, moreover, the transparency can be maintained almostcompletely. Therefore, the light emission that is generated with thesecond organic EL layer 703 b can be brought out, and the electricalcurrent efficiency can be doubled simply by doubling the electricalvoltage.

[0100] Moreover, since the entire process becomes consistent (forexample, when using low molecular materials, a dry process such asvacuum deposition can be used, and when using high molecular materials,a wet process such as spin coating can be used), the manufacturingprocess does not become cumbersome.

[0101] Note that, FIG. 7 shows the structure in which two of organic ELlayers have been provided. However, as described above, as long as asignificant amount of electrical voltage may be applied, the structuremay be multi-layered (of course, the conductive thin film layer isinserted between each of the organic EL layers). Therefore, the poorreliability of the organic semiconductor element, which is derived fromthe ultra thin film structure, can be overcome.

[0102] The philosophy described above naturally can also be applied inthe organic solar battery, which is said to utilize the oppositemechanism from the organic EL element. This will explained as follows.

[0103] It is assumed here that there is an organic solar battery S₁ inwhich a given light energy L₁ generates a photoelectric current with anelectrical current density J₁, thus generating an electromotive forceV₁. N number of the batteries S₁ are ohmically connected serially, andwhen a light energy nL₁ is irradiated there, n times the electromotiveforce (=nV₁) can be obtained if an equivalent light energy (=nL₁/n=L₁)can be provided to all the n number of solar batteries S₁. In short, ifall the organic solar batteries that are connected serially can absorbthe light, then the electromotive force increases as a product of thenumber of batteries.

[0104] For example, there is a report that discloses improving theelectromotive force by connecting two organic solar batteries serially(Reference 7: Masahiro HIRAMOTO, Minoru SUEZAKI, and Masaaki YOKOYAMA,“Effect of Thin Gold Interstitial-layer on the Photovoltaic Propertiesof Tandem Organic Solar Cell”, Chemistry Letters, pp. 327-330, 1990).According to Reference 7, by inserting a gold thin film between the twoorganic solar batteries (i.e., between a front cell and a back cell) aneffect of improving the electromotive force generated by the lightirradiation is obtained.

[0105] However, Reference 7 also structures the gold thin film to have athickness of 3 nm or less in order to achieve the transmittivity. Inother words, the film is structured as an ultra thin film that is thinenough for light to pass through it, designed so that the light willreach the back cell. Moreover, reproducibility becomes problematic whenthe thickness of the ultra thin film is on the order of several nm.

[0106] Such problems can also be resolved by using the presentinvention. That is, in the organic solar battery structure such asdisclosed in Reference 7, the present invention may be applied at thegold thin film portion. By doing this, the present invention can be usedas a single organic solar battery that is thicker and more highlyefficient than the conventional art, instead of connecting two elementsserially.

[0107] The basic concepts and structures of the present invention havebeen described above using the organic EL element and the organic solarbattery as examples. The following describes preferred examples ofstructures of the conductive thin film layer to be used for the presentinvention. However, the present invention is not limited to theseexamples.

[0108] First, various metallic thin films can be used because they areconductive, which is to say they have multiple carriers. Specifically,Au, Al, Pt, Cu, Ni, etc. are examples that can be used. Note that, whenthese metals are used for the conductive thin film layer, it ispreferable that they be formed as ultra thin films thin enough forvisible light to pass through (i.e., several nm to several tens of nm).

[0109] Further, various metallic oxide thin films can be used,particularly from the viewpoint of visible light transmittivity.Specific examples include ITO, ZnO, SnO₂, copper oxide, cobalt oxide,zirconium oxide, titanium oxide, niobium oxide, nickel oxide, neodymiumoxide, vanadium oxide, bismuth oxide, beryllium aluminum oxide, boronoxide, magnesium oxide, molybdenum oxide, lanthanum oxide, lithiumoxide, ruthenium oxide and BeO. Further, compound semiconductor thinfilms can also be used, including ZnS, ZnSe, GaN, AlGaN, and CdS.

[0110] A particular characteristic of the present invention is that theconductive thin film layer can be structured of an organic compound. Forexample, there is a technique for mixing a p-type organic semiconductorand an n-type organic semiconductor to form the semiconductor thin filmlayer.

[0111] Typical examples of a p-type organic semiconductor include, inaddition to CuPc represented by Chem. 1 below, phthalocyanine bound tothe other metals or bound to no metals (represented by Chem. 2 below).The following can be also used as the p-type organic semiconductor: TTF(represented by Chem. 3 below); TTT (represented by Chem. 4 below);methylphenothiazine (represented by Chem. 5 below); N-isopropylcarbazole(represented by Chem. 6 below); and the like. Further, a holetransporting material used for organic EL etc., such as TPD (representedby Chem. 7 below), α-NPD (represented by Chem. 8 below), or CBP(represented by Chem. 9 below) may be also applied thereto.

[0112] Typical examples of an n-type organic semiconductor include, inaddition to F₁₆—CuPc represented by Chem. 10 below, 3,4,9,10-perylenetetracarboxylic acid derivatives such as PV (represented by Chem. 11below), Me-PTC (represented by Chem. 12 below), or PTCDA (represented byChem. 13 below), naphthalenecarboxylic anhydrides (represented by Chem.14 below), naphthalenecarboxylic diimide (represented by Chem. 15below), or the like. The following can be also used as the n-typeorganic semiconductor: TCNQ (represented by Chem. 16 below); TCE(represented by Chem. 17 below); benzoquinone (represented by Chem. 18below); 2,6-naphthoquinone (represented by Chem. 19 below); DDQ(represented by Chem. 20 below), p-fluoranil (represented by Chem. 21below); tetrachlorodiphenoquinone (represented by Chem. 22 below);nickelbisdiphenylglyoxime (represented by Chem. 23 below); and the like.Further, an electron transporting material used for the organic EL etc.,such as Alq₃ (represented by Chem. 24 below), BCP (represented by Chem.25 below), or PBD (represented by Chem. 26 below) may be also appliedthereto.

[0113] Further, in another preferred technique, an organic compoundacceptor (electron acceptor) and an organic compound donor (electrondonor) are mixed and a charge-transfer complex is formed to make theconductive thin film layer to create conductivity to serve as theconductive thin film layer. The charge-transfer complex crystallizeseasily and is not easy to apply as a film. However, the conductive thinfilm layer according to the present invention may be formed as a thinlayer or in a cluster-shape (as long as the carriers can be injected).Therefore, no significant problems occur.

[0114] Representative examples of combinations for the charge-transfercomplex include the TTF-TCNQ combination shown in Chem. 27 shown below,and metal/organic acceptors such as K-TCNQ and Cu-TCNQ. Othercombinations include [BEDT-TTF]-TCNQ (Chem. 28 below), (Me)₂P-C₁₈TCNQ(Chem. 29 below), BIPA-TCNQ (Chem. 30 below), and Q-TCNQ (Chem. 31below). Note that, these charge-transfer complex thin films can beapplied either as deposited films, spin-coated films, LB film, polymerbinder dispersed films, or the like.

[0115] Further, as a structural example of a conductive thin-film layer,a technique of doping an acceptor or a donor into an organicsemiconductor to apply a dark conductivity thereto is preferably used.An organic compound having a π-conjugate system represented by aconductive polymer etc. may be used for the organic semiconductor.Examples of the conductive polymer include materials put into practicaluse, such as poly(ethylenedioxythiophene) (abbreviated to PEDOT),polyaniline, or polypyrrole, and in addition thereto, polyphenylenederivatives, polythiophene derivatives, and poly(paraphenylene vinylene)derivatives.

[0116] Also, when the acceptor is doped, it is preferable that a p-typematerial be used for the organic semiconductor. Examples of the p-typeorganic semiconductor may include those represented by Chems. 1 to 9 asdescribed above. At this time, Lewis acid (strongly acidic dopant) suchas FeCl₃ (III), AlCl₃, AlBr₃, AsF₆, or a halogen compound may be used asthe acceptor (Lewis acid can function as the acceptor).

[0117] Further, in the case where the donor is doped, it is preferableto use an n-type material for the organic semiconductor. Examples ofn-type organic semiconductors include the above-mentioned Chems. 10 to26 and the like. Then, for the donor, alkali metals such as representedby Li, K, Ca, Cs and the like, or a Lewis base such as an alkali earthmetal (the Lewis base can function as the donor) may be used.

[0118] More preferably, several of the structures described above can becombined to serve as the conductive thin film layer. In other words, forexample, on one side or both sides of an inorganic thin film such as theabove-mentioned metallic thin film, metallic oxide thin film, orcompound semiconductor thin film can be formed with a thin film in whicha p-type organic semiconductor is mixed with an n-type organicsemiconductor, or the charge-transfer complex thin film, or the dopedconductive high molecular thin film, or a p-type organic semiconductordoped with the acceptor, or an n-type organic semiconductor doped withthe donor. In such a case, it is effective to use the charge-transfercomplex thin film in place of the inorganic thin film.

[0119] Further, by layering the n-type organic semiconductor thin filmthat is doped with the donor and the p-type organic semiconductor thinfilm that is doped with the acceptor to have these serve as thesemiconductor thin film layer, it becomes a functional organicsemiconductor layer into which the holes and the electrons can both beinjected effectively. Furthermore, a technique is also considered inwhich the donor doped n-type organic semiconductor thin film and theacceptor doped p-type organic semiconductor thin film or laminated ontoone side or both sides of the thin film in which the p-type organicsemiconductor thin film and the n-type organic semiconductor thin filmare mixed together.

[0120] Note that, all the types of the thin film which are given aboveas structures for the above-mentioned semiconductor thin film layer donot need to be formed in film shapes, but rather they may be also formedas island shapes.

[0121] By applying the above-mentioned semiconductor thin film layer inthe present invention, it becomes possible to manufacture the organicsemiconductor element with high reliability and good yield.

[0122] As an example, the organic thin film layer of the presentinvention can be structured such that light emission is obtained byflowing the electric current, to thereby obtain the organic EL element.Thus, the organic EL element of the present invention is also effectivebecause the efficiency can also be improved.

[0123] When used in this way, the structure of the organic thin filmlayer (i.e., the organic EL layer) may be the organic EL element organicEL layer structure and constitute materials that are generally used.Specifically, many variations are possible such as a laminated structuredescribed in Reference 2 with the hole transporting layer and theelectron transporting layer, and a single-layer structure using thehigh-molecular compound, and the high efficiency element using lightemission from the triplet excited state. Further, as described above,the colors from each of the organic EL layers as different emissioncolors can be mixed as different colors to enable an application as along-life white color light emission element.

[0124] Regarding the anode the organic EL element, if the light is to bemade to exit form the anode side, then ITO (indium tin oxide), IZO(indium zinc oxide), and other such transparent conductive inorganiccompounds can be often used. An ultra thin film of gold or the like isalso possible. If the anode does not have to be transparent (i.e., inthe case where the light is made to exit from the cathode side), then ametal/alloy and or a conductive body which does not transmit light butwhich has a somewhat large work function may be used, such as W, Ti, andTiN.

[0125] For the organic EL element cathode, a metal or alloy with a smallnormal work function such as an alkali metal, alkali earth metal or rareearth metal is used. An alloy including these metallic elements may beused as well. For example, an Mg:Ag alloy, an Al:Li alloy, Ba, Ca, Yb,Er, and the like can be used. Further, in the case where the light is tobe made to exit from the cathode side, an ultra thin film made of themetal/alloy may be used.

[0126] Further, for example, by using the organic thin film layeraccording to the present invention as the structure that generates theelectromotive force by absorbing the light, the organic solar batterycan be obtained. Thus, the organic solar battery of the presentinvention is effective because it improves efficiency.

[0127] When structured in this manner, the structure of the functionalorganic thin film layer may use the structure and structure materialsthat are generally used in the functional organic thin film layer of theorganic solar battery. A specific example is the laminated structurewith the p-type organic semiconductor and the n-type organicsemiconductor, such as is described in Reference 3.

Embodiments

[0128] [Embodiment 1]

[0129] In accordance with the present embodiment, a specific examplewill be given of the organic EL element according to the presentinvention using the charge-transfer complex as the conductive thin filmlayer. FIG. 8 shows an element structure of the organic EL element.

[0130] First, on a glass substrate 801 on which ITO as an anode 802 isdeposited into a film with a thickness of about 100 nm,N-N′-bis(3-methylphenyl)-N,N′-diphenyl-benzidine (abbreviated to TPD) asthe hole transporting material is deposited by 50 nm to obtain a holetransporting layer 804 a. Next, tris(8-quinolinolato)aluminum(abbreviated to Alq) as a light emitting material having an electrontransporting property is deposited by 50 nm to obtain anelectron-transporting and light emitting layer 805 a.

[0131] A first organic EL layer 810 a is formed in the above manner.Thereafter, TTF and TCNQ are codeposited at a ratio of 1:1 as aconductive thin film layer 806, forming a layer with a thickness of 10nm.

[0132] After that, 50 nm of TPD is deposited as a hole transportinglayer 804 b, and deposited on top of this is 50 nm of Alq, which servesas an electron transporting layer/light emitting layer 805 b. Thus, asecond organic EL layer 810 b is formed.

[0133] Finally, as the cathode 803, Mg and Ag are codeposited at anatomic ratio of 10:1, and the cathode 803 is formed to have a thicknessof 150 nm, to thereby obtain the organic EL element of the presentinvention.

[0134] [Embodiment 2]

[0135] In accordance with this embodiment, a specific example is shownof an organic EL element of the present invention, in which an organicsemiconductor that is the same as used in the organic EL layer isincluded in the conductive thin film layer, and the acceptor and thedonor are doped to make the organic EL element conductive. FIG. 9 showsan example of an element structure of the organic EL element.

[0136] First, 50 nm of TPD for serving as the hole transport material isdeposited onto a glass substrate 901 which has approximately 100 nm ofITO serving as an anode 902. Next, 50 nm of Alq which serves as theelectron transporting light-emission material is deposited, and thisserves as an electron transporting layer/light emitting layer 905 a.

[0137] After a first organic EL layer 910 a is formed in this way, 5 nmof a layer 906 is codeposited with the Alq so that the donor TTFconstitutes 2 mol %. Then, 5 nm of a layer 907 is codeposited with theTPD so that the acceptor TCNQ constitutes 2 mol %, to serve as aconductive thin film layer 911.

[0138] After that, 50 nm of TPD is deposited as a hole transportinglayer 904 b, and deposited on top of this is 50 nm of Alq, which servesas an electron transporting layer/light emitting layer 905 b. Thus, asecond organic EL layer 910 b is formed.

[0139] Finally, as the cathode 903, Mg and Ag are codeposited at anatomic ratio of 10:1, and the cathode 903 is formed to have a thicknessof 150 nm, to thereby obtain the organic EL element of the presentinvention. The element can be manufactured simply by the organicsemiconductor in the organic EL layer as the material for structuringthe conductive thin film layer, and mixing the donor and acceptor, thusbeing extremely simple and effective.

[0140] [Embodiment 3]

[0141] In accordance with the present embodiment, a specific example isshown of a wet-type organic EL element, in which an electrical lightemitting polymer is used for the organic EL layer and the conductivethin film layer is formed of a conductive polymer. FIG. 10 shows anelement structure of the organic EL element.

[0142] First, onto a glass substrate 1001 on which ITO as an anode 1002is deposited into a film with a thickness of about 100 nm, a mixedaqueous solution of polyethylene dioxythiophene/polystyrene sulfonicacid (abbreviated to PEDOT/PSS) is applied by spin coating to evaporatemoisture, so that a hole injecting layer 1004 is formed with a thicknessof 30 nm. Next,poly(2-methoxy-5-(2′-ethyl-hexoxy)-1,4-phenylenevinylene) (abbreviatedto MEH-PPV) is deposited into a film with a thickness of 100 nm by spincoating to obtain a light emitting layer 1005 a.

[0143] A first organic EL layer 1010 a is formed in the above manner.Thereafter, a 30 nm film of PEDOT/PSS is applied by spin coating, toserve as a conductive thin film layer 1006.

[0144] Then, after that, a 100 nm film of MEH-PPV is applied by spincoating, to serve as a light emitting layer 1005 b. Note that, since theconductive thin film layer is made of the same material as the holeinjecting layer, this second organic EL layer 1010 b does not need ahole injecting layer formed to it. Therefore, in a case where a thirdand a fourth organic EL layer are to be laminated onto this, aconductive thin film layer PEDOT/PSS and a light-emission layer MEH-PPVcan be layered alternately according to extremely simple manipulations.

[0145] Finally, 150 mn of Ca is deposited as the cathode. On top ofthis, 150 nm of Al is deposited as a cap to prevent oxidization of Ca.

[0146] [Embodiment 4]

[0147] In accordance with the present invention, a specific example isshown of a organic solar battery of the present invention, in which amix of the p-type organic semiconductor and the n-type organicsemiconductor is applied as the conductive thin film layer.

[0148] First, 30 nm of CuPc, which is the p-type organic semiconductor,is deposited onto the glass substrate that has approximately 100 nm ofITO applied onto it as a transparent electrode. Next, 50 nm of PV, whichserves as the n-type organic semiconductor, is deposited, and CuPc andPV are used to form a p-n junction in the organic semiconductor. Thisbecomes a first functional organic thin film layer.

[0149] After that, CuPc and PV are codeposited at a 1:1 ratio as theconductive thin film layer to have a thickness of 10 nm. Further, 30 nmof CuPc is deposited, and on top of that 50 nm of PV is deposited,whereby creating a second functional organic thin film layer.

[0150] Finally, 150 nm of Au is applied as the electrode. The organicsolar battery structured as described above is extremely effectivebecause it can realize the present invention simply by ultimately usingonly two types of organic compounds.

[0151] By reducing the present invention to practice, it becomespossible to provide the organic semiconductor element which is highlyreliable and has good yield, without having to use the conventionalultra thin film. Further, particularly in the photoelectronic deviceusing the organic semiconductor, the efficiency of the photoelectronicdevice can be improved.

What is claimed is:
 1. An organic semiconductor element comprising: anorganic structure formed by sequentially laminating an n number offunctional organic thin film layers (where n is an integer equal to orgreater than 2) comprising a first through an n-th functional organicthin film layers between two electrodes, wherein a conductive thin filmlayer is formed between a k-th functional organic thin film layer (wherek is an integer of 1≦k≦(n−1)) and a (k+1)th functional organic thin filmlayer, and wherein each of the conductive thin film layers ohmicallycontacts with each of the functional organic thin film layer.
 2. Anorganic semiconductor element comprising: an organic structure formed bysequentially laminating an n number of functional organic thin filmlayers (where n is an integer equal to or greater than 2) comprising afirst through an n-th functional organic thin film layers between twoelectrodes, wherein a conductive thin film layer which includes anorganic compound is formed between a k-th functional organic thin filmlayer (where k is an integer of 1≦k≦(n−1)) and a (k+1)th functionalorganic thin film layer, and wherein each of the conductive thin filmlayers ohmically contacts with each of the functional organic thin filmlayer.
 3. An organic semiconductor element comprising: an organicstructure formed by sequentially laminating an n number of functionalorganic thin film layers (where n is an integer equal to or greater than2) comprising a first through an n-th functional organic thin filmlayers between two electrodes, wherein a conductive thin film layerwhich includes an organic compound is formed between a k-th functionalorganic thin film layer (where k is an integer of 1≦k≦(n−1)) and a(k+1)th functional organic thin film layer, and wherein each of theconductive thin film layers contains at least one of an acceptor and adonor for the organic compound.
 4. An organic semiconductor elementcomprising: an organic structure formed by sequentially laminating an nnumber of functional organic thin film layers (where n is an integerequal to or greater than 2) comprising a first through an n-thfunctional organic thin film layers between two electrodes, wherein aconductive thin film layer which includes an organic compound is formedbetween a k-th functional organic thin film layer (where k is an integerof 1≦k≦(n−1)) and a (k+1)th functional organic thin film layer, andwherein each of the conductive thin film layers contains both of anacceptor and a donor for the organic compound.
 5. An organicsemiconductor element according to claim 3 or 4, wherein a region of thefunctional organic thin film layer contacting the conductive thin filmlayer includes an organic compound that is the same as the organiccompound.
 6. An organic semiconductor element according to claim 4,wherein: the conductive thin film layer is structured by laminating afirst layer formed by adding an acceptor to the organic compound, and asecond layer is formed by adding a donor to an organic compound that isthe same as the organic compound; and the first layer is positionedcloser to a cathode side than the second layer.
 7. An organicsemiconductor element according to claim 6, wherein a region of thefunctional organic thin film layer contacting the conductive thin filmlayer includes an organic compound that is the same as the organiccompound.
 8. An organic semiconductor element according to claim 4,wherein: the conductive thin film layer is structured by laminating afirst layer formed by adding an acceptor to a first organic compound,and a second layer formed by adding a donor to a second organic compoundthat is different from the first organic compound; and the first layeris positioned closer to a cathode side than the second layer.
 9. Anorganic semiconductor element according to claim 8, wherein a region ofthe functional organic thin film layer contacting the first layerincludes an organic compound that is the same as the first organiccompound.
 10. An organic semiconductor element according to claim 8,wherein a region of the functional organic thin film layer contactingthe second layer includes an organic compound that is the same as thesecond organic compound.
 11. An organic semiconductor element accordingto any one of claims 1 through 4, wherein the functional organic thinfilm layer comprises a bipolar organic compound.
 12. An organicsemiconductor element according to any one of claims 1 through 4,wherein: the functional organic thin film layer has at least one holetransporting layer comprising a hole transporting material, and at leastone electron transporting layer comprising an electron transportingmaterial; and the hole transporting layer is positioned closer to ananode side than the electron transporting layer.
 13. An organicelectroluminescent element comprising: an organic structure which emitslight by making a current flow therein and is formed by sequentiallylaminating an n number of functional organic thin film layers (where nis an integer equal to or greater than 2) comprising a first through ann-th functional organic thin film layers between an anode and a cathode,wherein a conductive thin film layer is formed between a k-th functionalorganic thin film layer (where k is an integer of 1≦k≦(n−1)) and a(k+1)th functional organic thin film layer, and wherein each of theconductive thin film layers ohmically contacts with each of thefunctional organic thin film layer.
 14. An organic electroluminescentelement comprising: an organic structure which emits light by making acurrent flow therein and is formed by sequentially laminating an nnumber of functional organic thin film layers (where n is an integerequal to or greater than 2) comprising a first through an n-thfunctional organic thin film layers between an anode and a cathode,wherein a conductive thin film layer which includes an organic compoundis formed between a k-th functional organic thin film layer (where k isan integer of 1≦k≦(n−1)) and a (k+1)th functional organic thin filmlayer, and wherein each of the conductive thin film layers ohmicallycontacts with each of the functional organic thin film layer.
 15. Anorganic electroluminescent element comprising: an organic structurewhich emits light by making a current flow therein and is formed bysequentially laminating an n number of functional organic thin filmlayers (where n is an integer equal to or greater than 2) comprising afirst through an n-th functional organic thin film layers between ananode and a cathode, wherein a conductive thin film layer which includesan organic compound is formed between a k-th functional organic thinfilm layer (where k is an integer of 1≦k≦(n−1)) and a (k+1)th functionalorganic thin film layer, and wherein each of the conductive thin filmlayers contains at least one of an acceptor and a donor for the organiccompound.
 16. An organic electroluminescent element comprising: anorganic structure which emits light by making a current flow therein andis formed by sequentially laminating an n number of functional organicthin film layers (where n is an integer equal to or greater than 2)comprising a first through an n-th functional organic thin film layersbetween an anode and a cathode, wherein a conductive thin film layerwhich includes an organic compound is formed between a k-th functionalorganic thin film layer (where k is an integer of 1≦k≦(n−1)) and a(k+1)th functional organic thin film layer, and wherein each of theconductive thin film layers contains both of an acceptor and a donor forthe organic compound.
 17. An organic electroluminescent elementaccording to claim 15 or 16, wherein a region of the functional organicthin film layer contacting the conductive thin film layer includes anorganic compound that is the same as the organic compound.
 18. Anorganic electroluminescent element according to claim 16, wherein: theconductive thin film layer is structured by laminating a first layerformed by adding an acceptor to the organic compound, and a second layerformed by adding a donor to an organic compound that is the same as theorganic compound; and the first layer is positioned closer to a cathodeside than the second layer.
 19. An organic electroluminescent elementaccording to claim 18, wherein a region of the functional organic thinfilm layer contacting the conductive thin film layer includes an organiccompound that is the same as the organic compound.
 20. An organicelectroluminescent element according to claim 16, wherein: theconductive thin film layer is structured by laminating a first layerformed by adding an acceptor to a first organic compound, and a secondlayer formed by adding a donor to a second organic compound that isdifferent from the first organic compound; and the first layer ispositioned closer to a cathode side than the second layer.
 21. Anorganic electroluminescent element according to claim 20, wherein aregion of the functional organic thin film layer contacting the firstlayer includes an organic compound that is the same as the first organiccompound.
 22. An organic electroluminescent element according to claim20, wherein a region of the functional organic thin film layercontacting the second layer includes an organic compound that is thesame as the second organic compound.
 23. An organic electroluminescentelement according to any one of claims 13 through 16, wherein thefunctional organic thin film layer is composed of a bipolar organiccompound.
 24. An organic electroluminescent element according to any oneof claims 13 through 16, wherein: the functional organic thin film layerhas at least one hole transporting layer comprising a hole transportingmaterial, and at least one electron transporting layer comprising anelectron transporting material; and the hole transporting layer ispositioned closer to an anode side than the electron transporting layer.25. An organic electroluminescent element according to claim 23, whereinthe bipolar organic compound includes a high molecular compound having aπ-conjugate system.
 26. An organic electroluminescent element accordingto claim 23, wherein: the bipolar organic compound includes a highmolecular compound having π-conjugate system; and the conductive thinfilm layer includes a high molecular compound having a π-conjugatesystem.
 27. An organic electroluminescent element according to claim 23,wherein: the bipolar organic compound includes a high molecular compoundhaving a π-conjugate system, and the conductive thin film layer includesa conducting high molecular compound with an acceptor or a donor addedto it.
 28. An organic electroluminescent element according to claim 24,wherein the conductive thin film layer includes at least one of the holetransporting material and the electron transporting material.
 29. Anorganic electroluminescent element according to claim 24, wherein theconductive thin film layer includes both the hole transporting materialand the electron transporting material.
 30. An organic solar batterycomprising: an organic structure which generates an electromotive forceby absorbing light and is formed by sequentially laminating an n numberof functional organic thin film layers (where n is an integer equal toor greater than 2) comprising a first through an n-th functional organicthin film layers between two electrodes, wherein a conductive thin filmlayer is formed between a k-th functional organic thin film layer (wherek is an integer of 1≦k≦(n−1)) and a (k+1)th functional organic thin filmlayer, and wherein each of the conductive thin film layers ohmicallycontacts with each of the functional organic thin film layer.
 31. Anorganic solar battery comprising: an organic structure which generatesan electromotive force by absorbing light and is formed by sequentiallylaminating an n number of functional organic thin film layers (where nis an integer equal to or greater than 2) comprising a first through ann-th functional organic thin film layers between two electrodes, whereina conductive thin film layer which includes an organic compound isformed between a k-th functional organic thin film layer (where k is aninteger of 1≦k≦(n−1)) and a (k+1)th functional organic thin film layer,and wherein each of the conductive thin film layers ohmically contactswith each of the functional organic thin film layer.
 32. An organicsolar battery comprising: an organic structure which generates anelectromotive force by absorbing light and is formed by sequentiallylaminating an n number of functional organic thin film layers (where nis an integer equal to or greater than 2) comprising a first through ann-th functional organic thin film layers between two electrodes, whereina conductive thin film layer which includes an organic compound isformed between a k-th functional organic thin film layer (where k is aninteger of 1≦k≦(n−1)) and a (k+1)th functional organic thin film layer,and wherein each of the conductive thin film layers contains at leastone of an acceptor and a donor for the organic compound.
 33. An organicsolar battery comprising: an organic structure which generates anelectromotive force by absorbing light and is formed by sequentiallylaminating an n number of functional organic thin film layers (where nis an integer equal to or greater than 2) comprising a first through ann-th functional organic thin film layers between two electrodes, whereina conductive thin film layer which includes an organic compound isformed between a k-th functional organic thin film layer (where k is aninteger of 1≦k≦(n−1)) and a (k+1)th functional organic thin filn layer;and wherein each of the conductive thin film layers contains both of anacceptor and a donor for the organic compound.
 34. An organic solarbattery according to claim 32 or 33, wherein a region of the functionalorganic thin film layer contacting the conductive thin film layerincludes an organic compound that is the same as the organic compound.35. An organic solar battery according to claim 33, wherein: theconductive thin film layer is structured by laminating a first layerformed by adding an acceptor to the organic compound, and a second layerformed by adding a donor to an organic compound that is the same as theorganic compound; and the first layer is positioned closer to a cathodeside than the second layer.
 36. An organic solar battery according toclaim 35, wherein a region of the functional organic thin film layercontacting the conductive thin film layer includes an organic compoundthat is the same as the organic compound.
 37. An organic solar batteryaccording to claim 33, wherein: the conductive thin film layer isstructured by laminating a first layer formed by adding an acceptor to afirst organic compound, and a second layer formed by adding a donor to asecond organic compound that is different from the first organiccompound; and the first layer is positioned closer to a cathode sidethan the second layer.
 38. An organic solar battery according to claim37, wherein a region of the functional organic thin film layercontacting the first layer includes an organic compound that is the sameas the first organic compound.
 39. An organic solar battery according toclaim 37, wherein a region of the functional organic thin film layercontacting the second layer includes an organic compound that is thesame as the second organic compound.
 40. An organic solar batteryaccording to any one of claims 30 through 33, wherein the functionalorganic thin film layer is composed of a bipolar organic compound. 41.An organic solar battery according to any one of claims 30 through 33,wherein: the functional organic thin film layer has at least one holetransporting layer comprising a hole transporting material, and at leastone electron transporting layer comprising an electron transportingmaterial; and the hole transporting layer is positioned closer to ananode side than the electron transporting layer.
 42. An organic solarbattery according to claim 40, wherein the bipolar organic compoundincludes a high molecular compound having a π-conjugate system.
 43. Anorganic solar battery according to claim 40, wherein: the bipolarorganic compound includes a high molecular compound having a π-conjugatesystem; and the conductive thin film layer includes a high molecularcompound having a π-conjugate system.
 44. An organic solar batteryaccording to claim 40, wherein the bipolar organic compound includes ahigh molecular compound having a π-conjugate system, and the conductivethin film layer includes a conducting high molecular compound with anacceptor or a donor added to it.
 45. An organic solar battery accordingto claim 41, wherein the conductive thin film layer includes at leastone of the hole transporting material and the electron transportingmaterial.
 46. An organic solar battery according to claim 41, whereinthe conductive thin film layer includes both the hole transportingmaterial and the electron transporting material.
 47. Any one of anorganic semiconductor element, organic electroluminescent element and anorganic solar battery according to any one of claims 1 through 4, 13through 16, and 30 through 33, wherein a conductivity of the conductivethin film layer is equal to or greater than 10⁻¹⁰ S/m².
 48. Any one ofan organic semiconductor element, organic electroluminescent element andan organic solar battery according to any one of claims 1 through 4, 13through 16, and 30 through 33, wherein the conductive thin film layer isin a floating state.